Engineering

According to the data, 2.5 lakh students are nearly selected for JEE Advance 2019 but I think, nearly 1.7 lakh will give JEE Advance exam because of the matching date with other exams like WBJEE, etc. Also, JEE Advance is quite tougher as compared to other papers.

You do have chances of getting a seat in AEI or JEC. At AIR-4500 (ST-Category) you have good chances of getting seats in other good institutes, you can check the below link:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Yes, you will get a seat in Shiv Nadar University with this score. Last year, students with the same score got a seat in the same college.

I think Chandigarh University is the best option, but if you want to migrate, it is possible. You just need to consult regarding the same with the academic head of the institute which you desire to join.

Yes, you can get admission in Amrita University. Your rank is good enough to get you a seat in this college. You can apply with your category also to get reservations benefits. And keep all the documents ready for verification at the time of admission.
Best of luck.

Petroleum Engineering in Dibrugarh University will be difficult to get at this rank. Generally, the cut-off for it is around 50000. You can check below institutes for petroleum engineering:
Bhubaneswar Institute of Industrial Technology, Bhubaneswar
Samrat Ashok Technological Institute, Vidisha
University Institute of Technology RGPV, Bhopal
You can also check the below link for other colleges and branches:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

First of all, you have to tell your category then only anyone can give you a clear cut answer. So, I am assuming you to be of general category, with this rank, it is not possible for you to get any government college.
I hope it helps.
All the best.

You can see your score on the website of NTA:
https://jeemain.nic.in/jeemainresult/Root/AuthCandWithDob.aspx